Everything You Need to Know about Narcissists, Psychopaths, and Abuse - click on this link: http://www.narcissistic-abuse.com/faq1.html
There are numerous mechanisms, which mothers use to ensure the continued presence and emotional dependence of their offspring (of both sexes).
The mother can cast herself in the role of the eternal victim, a sacrificial figure, who dedicated her life to the child (with the implicit or explicit proviso of reciprocity: that the child dedicate his life to her). Another strategy is to treat the child as an extension of the mother or, conversely, to treat herself as an extension of the child.
Yet another tactic is to create a situation of shared psychosis or "folie a deux" (the mother and child united against external threats), or an atmosphere suffused with sexual and erotic insinuations, leading to an illicit psychosexual bonding between mother and child.
In this, latter case, the adult's ability to interact with members of the opposite sex is gravely impaired and the mother is perceived as envious of any feminine influence other than hers. Such a mother is frequently critical of the women in her offspring's life pretending to do so in order to protect him from dangerous liaisons or from ones which are "beneath him" ("You deserve more").
Other mothers exaggerate their neediness: they emphasise their financial dependence and lack of resources, their health problems, their emotional barrenness without the soothing presence of the child, their need to be protected against this or that (mostly imaginary) enemy. Guilt is a prime mover in the perverted relationships of such mothers and their children.
(From the book "Malignant Self-love: Narcissism Revisited" by Sam Vaknin - Click on this link to purchase the print book, or 16 e-books, or 3 DVDs with 16 hours of video lectures on narcissists, psychopaths, and abuse in relationships: http://www.narcissistic-abuse.com/thebook.html)